1. Field of the Invention
This invention relates generally to apparatus and methods of laser-assisted nanomanufacturing such as nanoscale machining, phase transformation, chemical reaction mediated processes (chemical vapor deposition or chemical etching) on the nanoscale using small probes and laser radiation. In particular, in some aspects the invention relates to laser-assisted nanomanufacturing and in situ monitoring methods and systems based on coupled optical near-fields to investigate nanoscale light-nanomaterials interactions.
2. Related Art
Traditional methods of material processing at the sub-micron scale involve indirect, multi-step processes that result in high manufacturing cost. The only direct-write technologies currently available are electron and ion beam writing. However, the minimum feature size for these methods is limited by the interaction volume of the incident electron or ion beams with the sample. Even though an electron beam can be focused to a spot of less than 1 nm for beam writing, the resulting scattering of the irradiated electrons and emission of secondary electrons from the sample leads to additional distribution of processed material on the order of 100 nm. Thus the minimum feature size achievable in direct-write methods is about 100 nm, too large for semiconductor industry needs. Currently, in order to achieve truly nanometer-scale device features, the semiconductor industry can use electron lithography. The minimum achievable line width of electron lithography has been shown to be about 10 nm. However, as with all lithographic processes, electron lithography has the disadvantage that it is an indirect process, and it is not possible to address individual structures easily. Furthermore, electron-beam, ion-beam, and imprinting technologies lack the flexibility to form three-dimensional nanostructures. Nanofabrication of complex two- or three-dimensional structures cannot be readily accomplished
Traditional electron microscopy techniques such as SEM and TEM have been adapted for nanoscale inspection (see, e.g., David C. Joy, Alton D. Romig, Joseph Goldstein, Principles of Analytical Electron Microscopy by Springer, 1986). In situ monitoring capabilities have also been demonstrated based on substrate heating, electric bias and/or a controlled gas environment. To date, nanoscale localization of events has been achieved by using a sharp tip inside the electron microscope. For example, as reported by Goldberg et al., In situ electrical probing and bias-mediated manipulation of dielectric nanotubes in a high-resolution transmission electron microscope, Appl. Phys. Lett., Vol. 88, 123101, 2006, an electrically biased tip has been used to localize and control carbon nanotube growth.
Near-field optics is that branch of optics that considers configurations that depend on the passage of light to, from, through, or near an element with subwavelength features and the coupling of that light to a second element located a subwavelength distance from the first. The barrier of spatial resolution imposed by the very nature of light itself in conventional optical microscopy contributed significantly to the development of near-field optical devices, most notably the near-field scanning optical microscope, or NSOM. The limit of optical resolution in a conventional microscope, the so-called diffraction limit, is on the order of half the wavelength of the light used to image. Thus, when imaging at visible wavelengths the smallest resolvable objects are several hundred nanometers in size. Using near-field optical techniques, researchers currently resolve features on the order of tens of nanometers in size. While other imaging techniques (e.g. atomic force microscopy and electron microscopy) can resolve features of much smaller size, the many advantages of optical microscopy make near-field optics a field of considerable interest.